Two-component heat developing diazotypes



United States Patent 3,379,531 TWO-COMPONENT HEAT DEVELOPING DIAZOTYPES Michael F. Mizianty, Bingharnton, Walter J. Welch, Port Dickinson, and John J. McKinney, Binghamton, N.Y., assignors to General Aniline & Film Corporation, New York, N .Y., a corporation of Delaware No Drawing. Filed Mar. 30, 1965, Ser. No. 444,073 18 Claims. (Cl. 96-91) This invention relates to two-component diazotype photoprinting materials susceptible to development on heating wherein said light-sensitive two-component diazotype layer comprises a neutral to acid reacting reagent yielding an alkaline reacting compound on heating and a diazonium salt of a diamine having the structure wherein Z is piperazino, piperidino or morpholino; R and R are hydroxyalkoxy, alkoxy or alkoxyalkoxy groups, at least one of which R and R groups are hydroxyalkoxy.

Two-component diazotype photoprinting material comprises a supporting sheet, such as paper or film, having in a surface coating or layer, an azo coupling component and a light-sensitive diazonium compound stabilized against premature coupling by inclusion of an acid stabilizer. On exposure of such coating to actinic light under an opaque pattern on a translucent background, the light-sensitive diazonium compound is destroyed in the light-struck areas and on subsequent exposure to an alkaline development medium, such as gaseous ammonia, the acid stabilizer is neutralized and the residual diazonium compound couples with the coupling component to form an azo dye image in the areas corresponding to the opaque portions of the original pattern. Photoprinting materials of this type have met with various objections, such as the inconvenience associated with alkaline development and the need for special equipment to avoid obnoxious ammonia odors.

It has been proposed to include in a two-component light-sensitive diazotype layer of the aforesaid nature, one or more reagents having an acid to neutral reaction which, on heating, are converted or decomposed to yield an alkaline reacting compound. Diazotype photoprinting materials containing such reagents can be developed after exposure to light under a pattern as mentioned above by heating at a temperature causing the aforesaid modification or decomposition. The alkaline reaction product thereby formed neutralizes the acid stabilizer and causes image-wise coupling of the residual diazonium compound with the azo coupling component. Premature coupling of the diazonium compound during storage has tended to destroy the desired contrast in many cases.

Numerous attempts have been made in the prior art to obviate some of these problems. Thus, it has been proposed to prepare and apply the individual diazotype and coupling materials to photographic sheets in such a manner that they will form azo dyes under heat alone. An example is contained in U.S.P. 2,418,623. This patent proposes to use a biguanidine salt and a diazo compound which would decompose under the influence of heat to yield ammonia as a developing agent. In U.S.P. 2,178,771 separate layers were proposed and development by use of steam was suggested. Various other patents have suggested other processes involving heat.

A number of other prior art investigators have sug gested that the diazonium salts and couplers might be developed by heat, provided they are applied in separate layers or coatings, the application of the separate coatings to be such as to axoid premature reaction between them. U.S.P. 3,046,128 discloses a typical heat developing twocomponent diazotype of this type wherein a light-sensitive diazonium layer is applied to one side of a fairly porous sheet of paper and an alkali generating layer is applied to the opposite side of the paper. The alkali generating layer contains materials having a vapor pressure such that at room temperature or slightly above room temperature the alkaline material has a low vapor pressure and at temperatures of about 200 to 400 F. the alkali material has substantial vapor pressure. The alkaline material either breaks down and passes as a vapor through the paper or merely passes through he paper without any chemical breakdown. Various materials such as urea, guanidine, alkyl substituted ureas, ammonia salts of Weak acid, volatile organic base (ethylenediamine) are suggested. Systems of this type have the disadvantage that the coupling rate of the diazotype components is relatively slow be cause of the slow rate at which the alkaline material reaches the reaction zone.

It has also been suggested in some instances that the alkaline material be physically separated in some manner and only brought together later for development purposes. U.S.P. 3,076,707 illustrates one method of accomplishing this. The patentees disclose forming a non-reactive crystalline complex of a basic material such as an amine, and a phenolic compound or urea, This crystalline complex is decomposed after exposure of the diazotype material by the influence of heat.

Each of these schemes however involves certain practical difficulties and none of them has been widely successful. Heating diazotype paper to to 200 C. cannot be carried out without causing some degradation of the diazo compound. Density and brightness of the image obtained is accordingly dependent upon the coupling speed of the diazonium compound, the speed with which the alkaline material is made available to promote the coupling reaction and the rate at which the diazonium compound is decomposed. It is accordingly desirable to use fast coupling diazotype components. However the faster the coupling speed of the components, the poorer the shelf life of the diazotype and the greater the tendency for background discoloration of the final print material.

The so-called high speed diazos of the 2,5-dialkoxy-4- morpholinobenzene diazonium salt type have not functioned well in these systems. These diazos have developed poorly, giving weak purple dyes. Further, the back ground areas of the sensitized base becomes heavily discolored following development. On the other hand the use of the less light-sensitive N,N-dialkylaminobenzenediazonium salt type does not yield images of optimum density at optimum printing speeds on commercially available printers. The object of this invention is to provide heat developing diazotypes based on high speed diazos which yield images of high density and a more desirable less purple color without background discoloration.

We have now found that the objects of our invention can be attained using diazonium salts of amines having the structure NH: where Z is morpholino, piperidino or piperazino; R and R are hydroxyalkoxy, alkoxy or alkoxyalkoxy and at least one of R and R are hydroxyalkoxy.

Diazonium salts corresponding to the above formula are described and claimed in commonly assigned copending application Serial No. 422,415, filed December 30, 1964. The disclosure of said application is hereby incorporated by reference.

In the above formula R and/or R can be hydroxyalkoxy such as Z-hydroxyethoxy, 2-hydroxypropoxy, 3- hydroxypropoxy, 4-hydroxybutoxy, etc.; alkoxyalkoxy such as Z-ethoxyethoxy, Z-ethoxypropoxy, 3-ethoxypropoxy, etc. and alkoxy such as methoxy, ethoxy, propoxy, butoxy, stearoxy, etc. Representative amines of the above formula include 2,5-di-(2-hydroxyethoxy)-4-morpholinoaniline, 2,5-di-(Z-hydroxyethoxy)-4-piperazinoaniline, 2,5-di-(2-hydroxyethoxy)-4-piperidinoaniline, 2,5-di- (Z-hydroxyethoxy) 4 methylpiperazinoaniline, 2-(2- hydroxyethoxy) -5-methoxy 4 morpholinoaniline, 2-(2- hydroxyethoxy) 5 butoxy-4-morpholinoaniline, 2-(2- hydroxyethoxy) 5 (Z-ethoxyethoxy)-4-morpholinoaniline, 2-methoxy-5-(Z-hydroxypropoxy)-4-morpholinoaniline, 2-butoxy-5-(B-hydroxypropoxy)-4-morpholinoaniline, etc.

The diazonium salts of the aforesaid amines are preferably employed in the form of their double salts with zinc chloride, tin chloride, cadmium chloride and the like.

Heat responsive reagents having an acid to neutral reaction at room temperature which are adapted to yield on heating to temperatures of 100 to 200 C., an alkaline reacting compound for neutralizing the acid in a lightsensitive photoprinting material of this invention include trichloroacetate and its derivatives which yield ammonium, nitrogen bases on heating, alkali metal salts of strong organic acids which are decomposed on heating to form basic compounds such as alkali metal salts of malonic, oxalic, maleic or benzene sulphinic acids; alkali metal salts of aliphatic monocarboxy acids of 1 to 3 carbon atoms having negative chain substituents such as halogen, CN or NO in alpha or beta positions; and of these, especially the alkali metal (e.g. Na, K), ammonium and nitrogen base salts of trichloroacetic acid.

Accelerators or auxiliary sources of alkali such as dicyandiamide and guanidine sulfate can be used advantageously with any of the aforesaid reagents having an acid to neutral reaction.

Azo coupling components which can be incorporated in the materials of the invention are for example 2-(m-hydroxyphenoxy)ethanol 2,3-dihydroxynaphthalene 1,8-dihydroxynaphthalene Phloroglucinol Resorcinol Octylresorcinol Alpha-resorcylamid 3-methyl-l-phenyl-S-pyrazolone Acetoacetanilide H-acid 2,3-dihydroxynaphthalene-6-sulfonic acid 2,5-xylenol 2-methyl resorcinol Acid stabilizers such as citric acid, tartaric acid, boric acid, acetic acid and similar acid reacting compounds are used to prevent premature coupling of the diazonium salt and azo coupling component.

In addition to the foregoing materials there can also be included reagents commonly employed in diazotype photoprinting materials, as for example, intensifiers such as ammonium sulfate, zinc chloride or nickel sulfate; stabilizing agents such as thiourea, or thiosinamine; accelerators such as 1-allyl-3-fl-hydr0xyethyl-thiourea or 1- allyl-thiourea; hygroscopic agents such as glycol or glycerin; and wetting agents such as saponin, lauryl sulfate, keryl benzene sulfonate or oleyl-N-methyltaurine; binders such as polyvinyl alcohol, starch polyvinyl acetate, etc.

The components of the sensitizing composition are preferably incorporated in a single solution or suspension and applied in a single coating step to the base. The latter may be paper, or film such as regenerated cellulose, cellulose acetate or other plastic films. However the various components of the sensitizing composition can be applied, if desired, in successive coatings-one containing, for example, the diazonium salt, and another the alkali generating heat-sensitive reagent, the azo coupling component being incorporated in either of the two layers.

The material coated in accordance with the invention is developed after exposure under an opaque pattern on a translucent background, by heating at temperatures between and 200 C., and preferably between 180 C., at which decomposition or conversion of the acid to neutral reagent to an alkaline reacting compound occurs. This promotes coupling of the residual diazonium compound with the azo coupling component.

The following examples are merely illustrative and should not be construed as limiting the scope of this invention:

EXAMPLE I A paper base was coated with the following heat developing sensitizing formulation:

Parts by weigh Citric acid 0.5 Sodium 6,7-dihydroxynaphthalene-Z-sulfonate 3 Magnesium chloride 0.5 Sodium trichloroacetate 3 Sodium 1,3,6-naphthalene trisulfonate 3 Polyvinyl alcohol 4 2 (2 hydroxyethoxy) 5 methoxy 4 morpholinobenzenediazonium chlon'de 0.5 Silica 4 Polyvinyl acetate emulsion 5 Water 100 The paper was dried and exposed to light under a translucent original bearing opaque image area. The exposed paper was developed by passing it through a heated chamber having temperatures of 120 to C. A blue dye of good density and brightness was formed in the image areas of the developed print. Control samples were run using the same amount of 2,5-diethoxy-4-morpholinobenzenediazonium chloride and 4-diethylaminobenzenediazonium chloride. The light-sensitive element prepared according to this invention yielded dye images having approximately 50% greater dye density as read on an Ansco Macbeth reflectance densitometer than the comparison samples.

Further, the light-sensitive compounds utilized in this invention yielded prints having much less background discoloration than the prints prepared with 2,5-dietboxy-4- morpholinobenzene diazos. In addition the light-sensitive elements of this invention have markedly greater light sensitivity than the 4diethylaminobenzenediazos.

The diazonium salt of 2-(2-hydroxyethoxy)-5-methoxy- 4-morpholinobenzenediazonium chlorostannate was prepared by (1) refluxing for 18 hours a mixture of 20.3 g. of 4-methoxy-3-bromophenol, 8.05 g. of 2-chloroetbanol in an aqueous alcoholic sodium hydroxide medium comprising 50 ml. ethanol, 4 g. sodium hydroxide and 10 ml..

water to form 5-(Z-hydroxyethoxy)-2-methoxy-1-bromobenzene, (2) reacting 38 g. of 5-(2-hydroxyethoxy)-2- methoxy-l-bromobenzene with 40 ml. 6MHNO in 300 ml. of acetic acid to form 2-(2-hydroxyethoxy)-5-methoxy-4-bromol-nitrobenzene, (3) refluxing 85 g. of 2-(2- hydroxyethoxy) 5 methoxy 4 bromo 1 nitrobenzene in 250 ml. morpholino for 5 hours to form 2-(2-hydroxyethoxy) 5 methoxy 4 morpholino 1 nitrobenzene, (4) shaking a mixture of 29.8 g. of Z-(Z-hydroxyethoxy)-5-methoXy-4-morpholino-1-nitrobenzene, 1.0 g. of 5% palladium on charcoal and 200 ml. ethanol under 50 psi. of hydrogen until the theoretical amount of hydrogen was absorbed necessary to reduce the nitro group to an amino group, (5) treating the reaction prod- EXAMPLE II A paper base was coated with the following heat developing sensitizing formulation:

Parts by weight Citric acid 0.5 Sodium 6,7-dihydroxynaphthalene-Z-sulfonate 3 Magnesium chloride 0.5 Sodium trichloroacetate 3 Sodium 1,3,6-naphthalene trisulfonate 3 Polyvinyl alcohol 4 2,5 di (2 hydroxethoxy) 4 morpholinobenzenediazonium chloride 0.5 Silica 4 Polyvinyl acetate emulsion 5 Water 100 The paper was dried and exposed to light under a translucent original bearing opaque image areas. The exposed paper was developed by passing it through a heated chamher having temperatures of 120 to 150 C. A blue dye of good density and brightness was formed in the image areas of the developed print. Control samples were run using the equivalent amount of 2,5diethoxy-4-morpholinobenzenediazonium chloride and 4-diethylaminobenzenediazonium chloride. The light-sensitive element prepared according to this invention yielded dye images having approximately 50% greater dye density as read on an Ansco Macbeth reflectance densitometer than the comparison samples. Further, the light-sensitive compounds utilized in this invention yielded prints having much less background discoloration than the prints prepared with 2,5-diethoxy-4-morpholinobenzenediazos. In addition the light-sensitive elements of this invention have markedly greater light sensitivity than the 4-diethylaminobenzenediazos.

The light-sensitive 2,5-di-(2-hydroxyethoxy)-4morpholinobenzenediazonium chloride utilized in this example was prepared in the manner described in Example V of copending application Ser. No. 422,415, filed Dec. 30, 1964.

Variations and modifications can be made in the procewherein Z is selected from the group consisting of piperazino, piperidino and morpholino; R and R are selected from the group consisting of alkoxy, hydroxyalkoxy, and alkoxyalkoxy groups, at least one of which R and R is hydroxyalkoxy.

2. Two-component diazotype photoprinting materials susceptible to development on heating, having on a surface of a support sheet a light-sensitive layer comprising an azo coupling component, a neutral to acid salt of a strong organic acid yielding an alkaline reacting compound on heating to a temperature between and 200 C., and a diazonium salt of a diamine having the structure wherein Z is selected from the group consisting of piperazino, piperidino and morpholino; R and R are selected from the group consisting of alkoxy, hydroxyalkoxy, and alkoxyalkoxy groups, at least one of which R and R is hydroxyalkoxy.

3. The article of claim 2 wherein both R and R are hydroxyalkoxy groups.

4. The article of claim 2 wherein at least one of R and R is hydroxyethoxy.

5. The article of claim 2 wherein Z is morpholino.

6. The article of claim 2 wherein one of R and R is an alkoxy group of from 1 to 4 carbon atoms.

7. The article of claim 2 wherein the diamine is 2,5- di- (Z-hydroxyethoxy -4-m0rpholinoaniline.

8. The article of claim 2 wherein the diamine is 2- 2-hydroxyethoxy -5-methoxy-4-morpholinoaniline.

9. The article of claim 2 wherein the neutral to acid salt of a strong organic acid comprises trichloroacetic acid.

10. A sensitizing composition for two-component diazotype printing materials susceptible to development on heating, comprising an aqueous medium, an azo coupling component, a neutral to acid reacting reagent yielding an alkaline reacting compound on heating to a temperature between 100 and 200 C., and a diazonium salt of a diamine having the structure wherein Z is selected from the group consisting of piperazino, piperidino and morpholino; R and R are selected from the group consisting of alkoxy, hydroxyalkoxy, and alkoxyalkoxy groups, at least one of which R and R is hydroxyalkoxy.

11. A sensitizing composition for two-component diazotype photoprinting materials susceptible to development on heating comprising an aqueous medium, an azo coupling component, a neutral to acid salt of a strong organic acid yielding an alkaline reacting compound on heating to a temperature between 100 and 200 C., and a diazonium salt of a diamine having the structure wherein Z is selected from the group consisting of piperazino, piperidino and morpholino; R and R are selected from the group consisting of alkoxy, hydroxyalkoxy, and alkoxyalkoxy groups, at least one of which R and R is hydroxyalkoxy.

12. The composition of claim 11 wherein both R and R are hydroxyalkoxy groups.

13. The composition of claim 11 wherein at least one of R and R is hydroxyethoxy.

14. The composition of claim 11 wherein Z is morpholino.

15. The composition of claim 11 wherein one of R and R is an alkoxy group of from 1 to 4 carbon atoms.

16. The composition of claim 11 wherein the diamine is 2,5-di-(Z-hydroxyethoxy)-4-morpholinoaniline.

17. The composition of claim 11 wherein the diamine is Z-(Z-hydroxyethoxy)-5-methoxy-4-morpholinoaniline.

18. The composition of claim 11 wherein the neutral to acid salt of a strong organic acid comprises trichloroacetic acid.

8 References Cited UNITED STATES PATENTS 2,286,701 6/1942 Werner 96-91 3,272,630 9/1966 Rauhut et a]. 96-91XR 3,281,245 10/1966 Werner et al 9691 3,298,834 1/1967 Eldred et al 9675 XR FOREIGN PATENTS 507,153 6/1939 Great Britain. 643,375 9/1950 Great Britain.

NORMAN G. TORCHIN, Primary Examiner.

C. BOWERS, Assistant Examiner. 

1. TWO-COMPONENT DIAZOTYPE PHOTOPRINTING MATERIALS SUSCEPTIBLE TO THE DEVELOPMENT ON HEATING, HAVING ON A SURFACE OF A SUPPORT SHEET A LIGHT-SENSITIVE LAYER COMPRISING AN AZO COUPLING COMPONENT, A NEUTRAL TO ACID REACTING REAGENT YIELDING AN ALKALINE REACTING COMPOUND ON HEATING TO A TEMPERATURE 100 AND 200*C., AND A DIAZONIUM SALT OF A DIAMINE HAVING THE STRUCTURE 